Aim: To date a vicariant event through the mutualistic relationship of a hylid frog and its bromeliad host found across two isolated mountain ranges as part of an island-continental split and to use this information to calibrate a molecular dating analysis of hylids. Location: South America. Time Period: Pliocene. Major Taxa Studied: Treefrogs, Arboranae. Methods: Pliocene tectonic movements sank a portion of a mountain range that connected present-day Trinidad (island) and northern Venezuela, eventually isolating populations of the golden tree frog Phytotriades auratus and its host bromeliad Glomeropitcairnia erectiflora on both sides of a saltwater barrier. We estimated the submersion rate timing of the vicariant event, then employed ecological niche modelling to establish the distribution of the frog and its host to the Pliocene. We generated nucleotide sequence data for the hylid on each side of the marine barrier and proposed a biogeographic calibration for the split between populations. Using Bayesian phylogenetic analysis, we evaluated the impact of incorporating this biogeographic calibration on estimates of treefrog divergence times. Results: A relatively continuous, high-elevation mountain range existed before the Pliocene and the opening of the Gulf of Paria (4.45 +/- 0.85 Ma). Phytotriades auratus and G. erectiflora would have been distributed across the Paria and Northern Range mountains as a single population since the Pliocene. Divergence times among treefrogs (Arboranae) were older than those inferred using fossil calibrations alone, with mean age estimates for subfamilies and genera being similar to 2 and similar to 1.2 million years older, respectively. Main Conclusions: Our study presents a biogeographic calibration based on a vicariant model that connects the evolution of the populations of a hylid through geology and ecological data. The implementation of this date as a molecular clock calibration reduces the uncertainty in date estimates for the shallower nodes in the phylogeny of Arboranae.

Abstract The Trinidad-Tobago archipelago contains two major islands and about 25 satellite islands ranging in size from 3.6 km2 to less than 1 ha. Despite different origins, both islands with satellites share a continental biota and have a rich snake fauna originating from vicariance and dispersal events. The authors used published molecular and morphological data to compare the two faunas and here discuss their origins and biogeography. Relatively high snake diversity and local endemics are present on both islands, which share some species with each other or with the mainland. Spatiotemporal distribution patterns illuminated by genetic clocks enhance understanding of evolution in the region and provide a more general example for the study of other biogeographic patterns. The authors also examined the literature for historical records. Trinidad shares many species with the Paria Peninsula in Eastern Venezuela, while Tobago species are more closely related to those from Venezuela’s more distant Central Caribbean Coastal Range.

In this paper we draw on the wealth of biological and geological knowledge derived from over a century of work on the rich fauna and complex geology of Trinidad and Tobago, and the surrounding region, through petroleum exploration, academic research, and other studies. We use molecular studies from the last 20 years that address biogeography, phylogeography, phylogenetics, population genetics, morphology, and biogeography to link biological events to the geology, neotectonics, and geomorphology of this area of the southeast Caribbean and northern South America. We focus on studies that provide molecular timings of speciation, vicariance, and dispersal events to compare these to geological data. We first develop and review two relatively clear-cut biology-geology connections; we then review and speculate on other possible yet-unknown connections.

Quantifying today's topography can provide insights into landscape evolution and its controls, since present topography represents a cumulative expression of past and present surface processes. The Ulsan Fault Zone (UFZ) is an active fault zone on the southeastern Korean Peninsula that was reactivated as a reverse fault around 5 Ma. The UFZ strikes NNW-SSE and dips eastward. This study investigates the relative tectonic activity along the UFZ and the landscape evolution of the hanging-wall side of the UFZ, focusing on neotectonic perturbations using 10Be-derived catchment-averaged denudation rates and bedrock incision rates, topographic metrics, and a landscape evolution model. Five geological segments were identified along the fault, based on their relative tectonic activity and fault geometry. We simulated four cases of landscape evolution to investigate the geomorphic processes and accompanying topographic changes in the study area in response to fault movement. Model results reveal that the geomorphic processes and the patterns of topographic metrics (e.g., chi anomalies) depend on inherited topography (i.e., the topography that existed prior to reverse fault reactivation of the UFZ). On the basis of this important model finding and additional topographic metrics, we interpret the tectono-geomorphic history of the study area as follows: (1) the northern part of the UFZ has been in a transient state and is in topographic and geometric disequilibrium, so this segment underwent asymmetric uplift (westward tilting) prior to reverse faulting on the UFZ around 5 Ma, and (2) its southern part was negligibly influenced by the asymmetric uplift before reverse faulting. Our study demonstrates the utility of topographic metrics as reliable criteria for resolving fault segments. Together with landscape evolution modeling, topographic metrics provide powerful tools for examining the influence of inherited topography on present topography and for the elucidation of tectono-geomorphic histories.

Coralsnakes of the genus Micrurus are a diverse group of venomous snakes ranging from the southern United States to southern South America. Much uncertainty remains over the genus diversity, and understanding Micrurus systematics is of medical importance. In particular, the widespread Micrurus nigrocinctus spans from Mexico throughout Central America and into Colombia, with a number of described subspecies. This study provides new insights into the phylogenetic relationships within M. nigrocinctus by examining sequence data from a broad sampling of specimens from Mexico, Guatemala, Honduras, Nicaragua, Costa Rica, and Panama. The recovered phylogenetic relationships suggest that M. nigrocinctus is a species complex originating in the Pliocene and composed of at least three distinct species-level lineages. In addition, recovery of highly divergent clades supports the elevation of some currently recognized subspecies to the full species rank while others may require synonymization.

The origin of relatively high topography in intraplate settings is elusive. The St. Francois Mountains, a tectonically inactive region with high relief, a Mesoproterozoic granite and rhyolite core, and Paleozoic sedimentary flanks, provide insights into the evolution of intraplate landscapes. We determined 14 in situ10Be exposure ages, 23 10Be catchment-wide denudation rates (CWDRs), and geomorphic indices using a geographic information system, and we modeled surface uplift using an isostatic-flexure model. CWDRs varied from ~5 to 10 ± 1.7 mm/k.y. and averaged 1.5 times greater in streams draining granite and rhyolite than in those draining flanking sedimentary rocks. In situ results from bedrock strath terraces gave Quaternary incision ages and incision rates that were tenfold higher than CWDRs. Major knickpoints (locally called shut-ins), all at 200 ± 70 m elevation, are located at contacts between the igneous and sedimentary rocks. Our exposure and denudation results inform isostatic-flexural modeling, which together support the conclusion that late Quaternary–Recent surface uplift driven by differential density and erosion focused in the igneous core is creating significant topography and relief in this intraplate setting.

The Northern Range of Trinidad is composed of Mesozoic passive margin sedimentary rocks that underwent ductile deformation and sub-greenschist- to greenschist-facies metamorphism in the early Miocene. Previous studies suggested a two-stage formation of the Northern Range between the Caribbean and South American plates: an initial collision drove mountain building in the Miocene and subsequent strike-slip plate motion preferentially exhumed the western segment, producing a westward increase in the metamorphic thermal gradient. However, these studies were not able to resolve whether this gradient was discrete or continuous so the tectonic model awaits testing. In this study we use Raman spectroscopy on carbonaceous material (RSCM), an empirical geothermometer, to constrain peak temperatures across the Northern Range with a greater resolution than was available in previous studies. The RSCM temperatures show an abrupt increase from 337 degrees C +/- 10 degrees C in the east to 442 degrees C +/- 16 degrees C west of Chupara Point, where a range-cutting fault (Chupara Fault) had been inferred in previous geologic mapping campaigns. Thus, the discrete thermal discontinuity of similar to 100 degrees C very likely represents the Chupara Fault. Our RSCM-derived peak metamorphic temperatures are 50 degrees C to 100 degrees C higher than those from previous estimates, requiring revision of tectonic models to account for deeper burial and greater exhumation. The peak metamorphic conditions determined here, and the deduced timing of faulting from published thermochronological data, are consistent with the two-stage tectonic model proposed in previous studies.

The NNW-SSE trending Manabhum Anticline is an impressive hill in the foredeep area of the Naga-Schuppen belt near Mishmi Hill on the southern bank of the Brahmaputra. We present a detailed geological study of this area to better establish its Quaternary tectonics. Rocks exposed in the core of the Manabhum anticline are Pleistocene in ages and Holocene sediments are also involved in the deformation. We have prepared a geological map at the 1:25,000 scale and for the first time dated nine representative samples of rocks and sediments from this area. Three distinct age ranges have been obtained; ~220 ka- ~130 ka, ~ 67 ka- ~36 ka, and less than 10 ka. We interpret the Manabhum Hill as an asymmetric antiformal fold that is actively developing in a compressive regime near the Eastern Himalayan Syntaxis (EHS) zone. We present evidence that it has been highly active tectonically during Pleistocene-Holocene time and maybe a key to understand how collision has accommodated and evolved in the eastern syntaxis.

Passive continental margins can show anomalously high topography and exhibit a discrete steep escarpment, divide, and gentle slope from the exterior to the interior of the margin. Compared with active (i.e. convergent and strike-slip) tectonic regions, the processes and rates of change of high-altitude landscapes driven by tectonics and/or climate in tectonically inactive (passive) continental margins are poorly understood. We used Be-10 catchment-wide denudation rates of fluvial sands (n = 29) collected in 17 catchments and 12 sub-catchments, as well as topographic analysis, to quantify the rate of landscape change along the western flank of the Taebaek Mountain Range (TMR). The denudation rates range from similar to 20 to similar to 70 mm/ka. These rates show no significant difference between upstream and downstream areas, implying that denudation is not (or is only negligibly) affected by deep-seated mass wasting processes and human impact. Be-10 denudation rates in the northern TMR are 1.6 times higher than in the south. In addition, the relationship between denudation rates and geomorphic parameter values also differs from north to south. These observed spatial differences in the rate of denudation and geomorphic response can be explained by intense frost weathering rather than lithological control. Our quantitative analysis of denudation rates and topography suggests that southwest-directed migration of the range's main divide occurs and that the range's western flank (low relief) is likely to be in a geomorphic state of quasi-equilibrium whereas the eastern flank (steep) still remains transient.

The islands of Trinidad and Tobago form a southern extension of the Lesser Antilles. Unlike the continental island of Trinidad, the more northerly Tobago formed as an older oceanic island volcanic arc. Their reptile biodiversity reflects colonization events from the South American mainland through land bridge connections at times of glacial maxima. Most of Tobago's herpetofauna has colonized through stepping-stone events from Trinidad. However, the enigmatic presence of a rare and poorly known fossorial snake in Tobago, Western Venezuela and Colombia, but absent in Trinidad and Eastern Venezuela, raises interesting questions regarding its biogeography, mode and timing of colonization of the island. Here, we sequence for the first time gene fragments from three individuals from Western Venezuela and one from Tobago and include them in the largest phylogeny of Atractus to date. We validate the monophyly of the species based on morphology and molecular data, with an unexpected low genetic divergence between island and mainland specimens. Despite more than 1000 km separating them, our time tree indicates a mean 550,000 year divergence. We examine alternative scenarios to explain the biogeography and conclude on an ancient corridor of coastal land bridges at times of very low (>100 m) sea-level falls that connected Venezuela to Tobago.

Plate corners that transition from subduction to transform motion can result in complex deformation. The southeastern corner of the Caribbean plate is a site where active westward subduction of the oceanic South American plate transitions to transform motion along continental South America. The Northern Range (Trinidad) and Paria (Venezuela) metamorphic mountains are located directly above this eastward propagating plate transition zone. We examined the exhumation history of the Northern Range and eastern Paria using apatite fission track (AFT) and apatite and zircon (U‐Th)/He (AHe and ZHe, respectively) thermochronology on 21 bedrock samples. These samples yield ages of ∼43–6 Ma (ZHe: aliquots), ∼20–4 Ma (AFT: pooled) and ∼5–2 Ma (AHe: aliquots). Along strike of the mountains, our new and published samples show a gradual eastward increase in age. Thermal modeling reveals two phases of rapid cooling and inferred exhumation that post‐dates oblique collision and that migrated from west to east. We record an ∼six‐fold increase in cooling and exhumation between ∼13–9 Ma in the Paria Peninsula and western Northern Range; a deceleration followed this rapid exhumation at ∼7 and 5 Ma. Synchronous with the deceleration in the west, exhumation of the eastern Northern Range increased ∼4 Ma. These post‐collisional changes in exhumation constrain the inversion to east‐side‐up tilting of the Northern Range to ∼4 Ma. We interpret the timing and pattern of exhumation since the mid‐Miocene to be consistent with the time‐transgressive processes produced by an eastward propagating lithospheric subduction‐transform edge propagator fault.

Faidherbiaalbida is an agroforestry tree species playing important agroecological and socioeconomic roles in arid and semiarid zones in Africa. For many years, anthropogenic and abiotic stresses were considered as the main threats for the species in West African parkland agroforests. Considerable dieback has recently occurred in F. albida trees of parkland agroforests in central southwestern Niger, and the causes are unknown. The objectives of this study are to (i) investigate the magnitude of dieback of F. albida trees and (ii) assess local community perceptions of the effects of F. albida dieback on crop production. The health status and phenology of 213 F. albida trees were observed in the area where the dieback is occurring. Similarly, a sample of 144 people, 86% of which were farmers, was surveyed. Dieback incidence of F. albida trees was 19%, with mortality of 6%. Large-diameter trees had greater dieback than small-diameter trees. The most affected parts of the tree were the branches at 54% and the trunks at 39%. The populations noted a 33–55% reduction in the yields of major crops. This dieback of F. albida trees poses a serious threat to the survival of rural communities. Further studies can be conducted to identify the cause or cause of the dieback to guide the suitable agroforestry parkland management strategies.

We examine, for the first time, biogeographic patterns in a series of tropical montane coastal systems in northern South America. We use amphibians and reptiles, which constitute the most critical communities based upon the prevalence of endemic taxa, to assess the region’s biodiversity. The montane coastal system spans an east-west distance of 925 km. It includes peaks ranging from 549 m to 2765 m above sea level and encompasses the montane complexes of northern Venezuela (including Isla de Margarita), an outlier at Santa Marta (Colombia), and ranges on the islands Trinidad and Tobago. The area supports 14 family level amphibian clades and 23 family level reptile clades. Fieldwork, museum specimen surveys, and a literature review suggest that biodiversity decreases at higher elevations. Here we examine the biogeographic patterns in the region to assess the role of the montane systems as possible refugia. We also look at the possible island and sky island effects using data from altitudes >200 m. At lower elevations, we tabulated 294 species, comprising 112 amphibians and 182 reptiles. About 45% of these taxa are endemic or exclusive to different sub-regions. At mid-elevation montane cloud forests, we find a much-reduced biodiversity with a total of 125 species (66 amphibians and 59 reptiles) exclusive or restricted to the region, and few species shared between systems. We find that biogeographical patterns follow a natural topographic disposition above 200 m in elevations. At the lower elevation cut off, there are 118 species (26 amphibians and 92 reptiles) shared among two or more of the studied mountain systems, suggesting a common origin and dispersal events, despite what seem to be topographic barriers. Biogeographical relationships support a topographic disposition of the region with close associations between the islands of Trinidad and Tobago, the Paria Range and the Turimiquire Massif, and close associations between the Sierra Nevada de Santa Marta and the Sierra de San Luis. Overall, the biogeographic relationships between amphibians and reptiles are similar. Species diversity in the eastern Caribbean region is less rich than in the west. This study includes the first herpetological surveys at the two easternmost mountains (Cerro La Cerbatana and Campeare) belonging to the Paria Range biogeographic unit, and aims to contribute to a better understanding of the rich biodiversity of the region.

We combine Global Positioning System and Interferometric Synthetic Aperture Radar (InSAR) data to characterize the interseismic behavior (i.e., locked or creeping), and strain partitioning for the faults along the Caribbean‐South American transform plate boundary. Interseismic strain is distributed mainly on three faults, the San Sebastian, El Pilar, and Central Range faults, but partitioning occurs across multiple faults in the west (San Sebastian and La Victoria faults) and east (Sub‐Tobago Terrane, Central Range, and South Coast faults). In northern Venezuela, slip is partitioned on the San Sebastian (16.4 ± 1.7 mm/yr) and La Victoria (4.3 ± 0.9 mm/yr) faults. In north‐eastern Venezuela, the El Pilar fault accommodates slip at a rate of 18.6 ± 1.8 mm/yr. In Trinidad and Tobago, slip is partitioned between the Sub‐Tobago Terrane (3.0 ± 0.1 mm/yr), Central Range (14.5 ± 2.0 mm/yr), and South Coast (3.0 ± 0.1 mm/yr) faults. The La Victoria, San Sebastian, the western El Pilar segment, and Sub‐Tobago Terrane faults are locked to depths of 16.2 ± 4.0 km, 7.7 ± 5.2 km, 6.7 ± 2.8 km, and 8.0 ± 0.2 km, respectively. The eastern segment of the El Pilar, the Central Range, and the South Coast faults all creep. Our new InSAR results indicate that the entire Central Range Fault is creeping. The locked western segment of this transform plate boundary is capable of producing a M w 8 earthquake, which is a significant finding regarding seismic hazard and risk.